Method of and means for utilizing thermionic currents



H. D. ARNOLIL.

METHOD OF AND MEANS FOR UTILIZING THERMIONIC CURRENTS,

APPLICATION FILED MAR. 20. I916. RENEWED MAY 16. ms.

1 349, 25 2 Patented Aug. 10, 1920.

I VIIIIHIYI ln ven for: Hare/d 0. Arnold UNITED STATES PATENT OFFICE.

HAROLD D, ARNOLD, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERNELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEWYORK.

METHOD OF AND MEANS FOR UTILIZING THERMIONIC GURRENTS.

Specification of Letters Patent.

Patented Aug. 10, 1920.

Application flled' March 20, 1916, Serial No. 85,362. Renewed May 16,1918. Serial No. 235,043.

To all whom it may concern Be it known that I, HAROLD DEFOREST ARNOLD, acitizen of' the United States, residing at East Orange, in the county ofEssex and State of New Jersey, have invented certain new and usefulImprovements in Methods of and Means for Utilizing Thermionic Currents,of which the following is a full, clear, concise, andkexact description.

This invention relates 0 thermionic amplifiers, and more particularly tocircuit arrangements by which the current iroltage characteristic ismade to have a desired form.

An object of the invention is to repeat or amplify electrical impulsessubstantially without distortion.

This-is accomplished by providing a thermionic'device wherein the curvewhich represents the relation between the input voltage and the outputcurrent is approximately straight.

A further object of the invention is to efficiently transfer electricalimpulses, employing a thermionic device.

This is accomplished by properly proportioning the internal outputcircuit impedance with respect to the external output circuit impedanceof the thermionic device.

This invention will be explained more in detail in connection with thedrawings in. which Figure 1 represents a thermionic amplifier and itscircuit, and Fig. 2 a curve by means of which its operation will be expained. Figs-3 re resents the same thermionic element modified inaccordance with this invention, and Fig. 4 a curve which will be used toexplain its operation. Fig. 5 represents another modified circuit forthe thermionic element of Fi 1.

Referring to Fig. 1, a t ermionic vacuum tube is shown containing thefilament F, input electrode or grid G, and anode or plate P. In theinput circuit of this ele ment is laced a battery C, whose function isto malntain the. electrode G at a negative potential with respect to thefilament and also to aid in fixing the point on the characteristic atwhich the amplifier is to be worked. The ob'ect of maintaining the gridnegative wit respect to the filament is to insure that no current shallflow from grid to filament and consequently that the input circuit shallhave a very ;h1gl1 resistance which shall be independent of the inputvoltage. The battery B in the output circuit serves to provide the spacecurrent from anode P to cathode F, whose variation is utilized toproduce the amplified signals.

F,-ig. 2 represents the operation of the ainplifier 0t Fig. 1. In thisfigure abscissae E,.'represent voltages of the battery C, and ordinatesI represent values of current in the output circuit. The curve shown isthe one which is obtained with the amplifier as used in ordinaryoperation, and it will be noted that its curvature is sufliciently lar eto produce distortion or rectification in t e signals produced by a-variation of input voltage E An object of this invention is to renderthe characteristic of Fig. 2 approximately straight throughout theoperating range while maintaining the ratio of amplification at asufficiently large value.

Fig. 3 shows the amplifier of Fig. 1 connected in amodifiedcircuit. Inthis figure an additional resistance R has been shown added in theoutput circuit and the electromotive force of the battery B has beenmodified in accordance with conditions to be explained later. Theelectromotive force of the battery C may also need to be modified. Thecurve in Fig. 4 shows the form of the characteristic when these changeshave been made. If in the amplifier of Fig. 1 a resistance Rapproximately equal to the normal internal resistance of the tube isadded in the output circuit, the effect will be to render thecharacteristic approximately straight but at the same time to greatlylower the current which flows in the output circuit. To raise thiscurrent to its normal operating level, it will be necessary to increasethe electro'inotive force of the battery B, and therefore to increasethe space current. It is therefore necessary, in order to secure anapproximatel straight characteristic and also a desire value of outputcurrent, to insert in the output circuit a resistance of the order of maitude of the internal resistance of the tu and at'the same time to varythe electromotive force of battery B in order that the output currentmay remain fixed at a predetermined value. When these adjustments. havebeen made, operation wil take place at an approximately straight part ofthe characterput circuit and istic curve and to the left of the currentaxis in the region of constant input impedance, and at the same time theratio of amplification is maintained suiliciently high.

While the resistance has been shown as connected directly in the outputcircuit of Fig. 3, it is to be understood that the invention is broaderthan this and that the re sistance may be inserted in other ways. Itmay, for example, be carried into this output circuit by means of atransformer. That is, if as shown in Fig. 5, the resistance R, isactually included in the secondary circuit of the output transformer, itwill produce an effective resistance in the primary circuits yielding,same result as if a resistance had been actually placed in this primarycircuit. The value of the effective resistance produced in said primaryby a given resistance in the secondary circuit will, of course, dependon the ratio of transformation of theotransformer.

What is claimed is:

1. A thermionic amplifier having an input circuit and an output circuit,a source of electromotive force in each of said circuits, and aresistance in said output circuit, the ma nitude of said electromotiveforces and 0 said resistance being so related that the output currentshall vary approximately linearly as the input voltage over a portion ofthe characteristic curve suitable for eflicient'operation of saidamplifier.

2. A thermionic amplifier having an input circuit and an output circuit,a source of electromotive force in each of said circuits, and aresistance in said output circuit, said resistance being of such a.magnitude that the output current shall vary approximately linearl asthe input voltage and said electromotive forces bein of such a magnitudeas to secure a desired value of said output current.

3. A thermionic amplifier having an input circuit andan output circuit,a source of electromotive force in each of said circuits, and aresistance in said output circuit, said resistance being of such a magnitude that the output current shall var approximately linearly as theinput vo tage, said electromotive forces being of such a ma nitude as tosecure a desired value of sai output current, and to maintain a highinput circuit impedance.

4. A thermionic amplifier having an inan output,circuit, a source ofelectromotive force in each of said circuits, and a resistance in saidoutput circuit, said resistance being approximately equal to the normalinternal resistance of the tube for the purpose set forth.

5. A thermionic amplifier having an input circuit and an output circuit,a source to all intents and purposes, the

the tube whereby the output current shall vary approximately linearly asthe input voltage, said electromotive forces being of such magnitudes asto secure a desired value of said output current, and'to maintain a highinput circuit impedance.

, (5. A thermionic device having an input circuit and .an outputcircuit, a resistance in said output circuit, said resistance being ofthe same order of magnitude as the internal impedance of the saiddevice.

7. A thermionic device having an input circuit and an output circuit,the resistance of said output circuit external to said device being ofthe same order of magnitude as the internal impedance of the saiddevice.

8. A thermionic device having an input circuit and an output circuit, aresistance in said output circuit external to said device, saidresistance being of the same magnitudeas the internal impedance of thesaid device.

9. A thermionic repeater having cathode,

, anode and' control electrodes, means for supplying current betweensaid cathode and anode, means connected to said cathode and controlelectrode for impressing thereon alternating currents to be repeated,and an output circuit connected to said cathode and anode, said outputcircuit having an impedance such that said alternating currents arerepeated substantially without distortion.

10. A thermionic device wherein the curve which represents therelationbetween input voltage and output current is approximately straight.

11. A thermionic repeater having an input circuit and an output circuit,said output circuit external to said repeater havin an impedance suchthat the curve whic represents the relation. between input voltage andoutput current is approximately straight.

12, A thermionic repeater having an input and\a n output circuit, saidoutput circuit externalto said repeater having an. impedance of the sameorder of ma n'ltude as the internal impedance of the sai repeater.

13. A thermionic repeater having an input and an output circuit, saidvoutput circuit external to said repeater having a resistance at least aslarge as the internal impedance of the said repeater.

14. A thermionic repeater having an input and an output circuit, saidoutput circuit external to said repeater having an impedance at least aslarge as the internal impedance of the said repeater.

15. A thermionic repeater having an input circuit and an output circuit,a source of electromotive force in each of said circuits, said outputcircuit havin an impedance, the magnitude of said e ectromotive forcesand said impedance being such as to cause the output current to varyapproximately linearly as the input voltage over a portion of thecharacteristic curve suitable for efficient operation of the saidrepeater.

16. A thermionic device having an input circuit and an output circuit,means for maintaining substantially an infinite impedance for said inputcircuit, the curve which represents the relation between the inputvoltage and output current of said device being approximately straight.

17. A thermionic amplifier having cathode, anode and control electrodes,means for supplying between said cathode and anode a current thevariation of which with voltage is substantially constant, meansconnected to said cathode and control electrode for impressing thereonalternating currents to vary the discharge between cathode and anodewithin a range corresponding to that part of the volt-amperecharacteristic of said amplifier that exhibits no substantial departurefrom a straight line, and an output circuit connected to said cathodeand anode. i

18. The method wherein is employed a thermionic device comprising a hotcathode and a control electrode for amplifying a variable electriccurrent without distortion which comprises producing from said cathodean electron discharge the variation of which with voltage issubstantially constant, and applying the input current to producecorresponding electromotive forces across said cathode and said controlelectrode, thereby varying said discharge within the range'for which theratio of current increment to voltage increment remains substantiallyconstant.

19. The method wherein is employed a thermionic device com rising a hotcathode and a grid for ampli ying a variable electric current withoutdistortion which comprises producing from said cathode an electrondischarge the variation of which with voltage is substantially constant,substantially infinitely impeding the input current and applying theinput current to produce corresponding electromotive forces across saidcathode and said grid, thereby var ing said discharge within the rangewhich the ratio of current increment to voltage increment remainssubstantially constant. V

In witness whereof I hereunto subscribe my name this 18th day of March,A. D. 1916.

HAROLD D. ARNOLD.

